Messages in this thread Patch in this message | | | Date | Thu, 11 Jan 2024 15:57:28 -0800 | Subject | Re: [PATCH v4 5/6] add listmount(2) syscall | From | Guenter Roeck <> |
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On 1/11/24 12:14, Linus Torvalds wrote: > On Thu, 11 Jan 2024 at 10:57, Guenter Roeck <linux@roeck-us.net> wrote: >> >> Any variance of put_user() with &buf[ctr] or buf + ctr fails >> if ctr is a variable and permitted to be != 0. > > Crazy. But the 64-bit put_user() is a bit special and tends to require > more registers (the 64-bit value is passed in two registers), so that > probably then results in the ICE. > > Side note: looking at the SH version of __put_user_u64(), I think it's > buggy and is missing the exception handler for the second 32-bit move. > I dunno, I don't read sh asm, but it looks suspicious. >
I wonder if something may be wrong with the definition and use of __m for u64 accesses. The code below also fixes the build problem.
But then I really don't know what
struct __large_struct { unsigned long buf[100]; }; #define __m(x) (*(struct __large_struct __user *)(x))
is supposed to be doing in the first place, and I still don't understand why the problem only shows up with CONFIG_MMU=n.
Guenter
--- diff --git a/arch/sh/include/asm/uaccess_32.h b/arch/sh/include/asm/uaccess_32.h index 5d7ddc092afd..f0451a37b6ff 100644 --- a/arch/sh/include/asm/uaccess_32.h +++ b/arch/sh/include/asm/uaccess_32.h @@ -196,7 +196,7 @@ __asm__ __volatile__( \ ".long 1b, 3b\n\t" \ ".previous" \ : "=r" (retval) \ - : "r" (val), "m" (__m(addr)), "i" (-EFAULT), "0" (retval) \ + : "r" (val), "m" (*(u64 *)(addr)), "i" (-EFAULT), "0" (retval) \ : "memory"); }) #else #define __put_user_u64(val,addr,retval) \ @@ -218,7 +218,7 @@ __asm__ __volatile__( \ ".long 1b, 3b\n\t" \ ".previous" \ : "=r" (retval) \ - : "r" (val), "m" (__m(addr)), "i" (-EFAULT), "0" (retval) \ + : "r" (val), "m" (*(u64 *)(addr)), "i" (-EFAULT), "0" (retval) \ : "memory"); }) #endif
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